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SVTPerformance's Chain of Restaurants
Tuning À la carte
Dies on Return to Idle
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<blockquote data-quote="Bullitt5566" data-source="post: 15762133" data-attributes="member: 119066"><p>I wanted to provide another update on this issue. I put the cams back in and worked on the tune again. The dashpot settings help, but I don't think they are the problem. I set the tune to idle in open loop and then leaned out the A/F by 10%. This helped a lot but the problem is still there. The engine stumbles when returning to idle.</p><p></p><p>I data logged Air/fuel from the wideband. I noticed that at idle the A/F is ~1.05 and open loop. A quick rev and the ecu goes closed loop and A/F is ~1.0. On return to idle the A/F goes dead rich ~.80 or more until the ecu goes open loop and the A/F recovers. If I force open loop and check the A/F everything is spot on at ~1.0 throughout the rpm range.</p><p></p><p>The key has been to keep the engine in open loop at idle. I've set it up in two places. Open loop RPM and TP, and Open loop at low loads. The latter required changing a time and vehicle speed scalars to 0. So basically the ecu drops into open loop when closed TP and RPM below 1200 and when load is below .20 returning to idle.</p><p></p><p>This masks the problem by making the transition to open loop idle faster, but it still doesn't answer why it spikes pig rich when transitioning to idle.</p></blockquote><p></p>
[QUOTE="Bullitt5566, post: 15762133, member: 119066"] I wanted to provide another update on this issue. I put the cams back in and worked on the tune again. The dashpot settings help, but I don't think they are the problem. I set the tune to idle in open loop and then leaned out the A/F by 10%. This helped a lot but the problem is still there. The engine stumbles when returning to idle. I data logged Air/fuel from the wideband. I noticed that at idle the A/F is ~1.05 and open loop. A quick rev and the ecu goes closed loop and A/F is ~1.0. On return to idle the A/F goes dead rich ~.80 or more until the ecu goes open loop and the A/F recovers. If I force open loop and check the A/F everything is spot on at ~1.0 throughout the rpm range. The key has been to keep the engine in open loop at idle. I've set it up in two places. Open loop RPM and TP, and Open loop at low loads. The latter required changing a time and vehicle speed scalars to 0. So basically the ecu drops into open loop when closed TP and RPM below 1200 and when load is below .20 returning to idle. This masks the problem by making the transition to open loop idle faster, but it still doesn't answer why it spikes pig rich when transitioning to idle. [/QUOTE]
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SVTPerformance's Chain of Restaurants
Tuning À la carte
Dies on Return to Idle
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